Immune-mediated abortion is an important, although poorly understood and often unrecognized, cause of pregnancy failure in women. Both spontaneous abortion and preeclampsia, which is associated with abnormal placentation, occur at increased frequency in human and bovine pregnancies established by assisted reproductive technologies such as in vitro fertilization (IVF). Our long-term goals are to understand the immunological basis of immune-mediated abortion and placental insufficiency, and to develop and test strategies to down-regulate the immune response to the conceptus. A unique bovine model of immune- mediated abortion and placental insufficiency based on the routine occurrence of inadequate placental development and fetal loss in bovine somatic cell nuclear transfer (SCNT) pregnancies will be used. Several observations support the validity of this model: (1) placental trophoblast cells of SCNT fetuses, in contrast to control fetuses, express classical major histocompatibility complex class I (MHC-I) antigens early in pregnancy, (2) T lymphocytes accumulate in the uterine stroma of SCNT recipients, and (3) MHC homozygous SCNT fetuses fare better than MHC heterozygous fetuses. These findings suggest that much of the fetal loss in SCNT pregnancies is due to immune-mediated abortion. This project is based on the general hypothesis that inappropriate trophoblast MHC-I expression early in pregnancy will induce immune-mediated abortion or placental insufficiency. Inappropriate expression of MHC-I proteins may consist of increased expression of classical MHC-I proteins, decreased expression of non-classical MHC-I proteins or a combination of the two. The proposal's specific aims are: (1) produce 8-10 MHC-I compatible SCNT, 8-10 MHC-I incompatible SCNT and 8-10 control pregnancies for collection of uterine and placental tissues on days 32 to 34 of pregnancy, and compare trophoblast MHC-I expression, uterine leukocyte populations and uterine and placental gene expression in the three types of pregnancies;and (2) compare embryonic mortality rates of SCNT embryos transferred into MHC-I compatible and incompatible recipient cows to determine if immune-mediated abortion can be avoided by eliminating the antigenic, MHC-I trigger. This project will elucidate the functional genomics of the cross-talk between the placenta and uterine immune system in normal and abnormal pregnancies. Functional genomics and morphological data will be integrated to create a complete picture of the cellular and molecular events involved in an important clinical problem: immune-mediated abortion. The project will also directly test the hypothesis that abnormal MHC-I expression early in pregnancy triggers immune-mediated abortion, a long-standing hypothesis that has never been adequately tested because of lack of a suitable animal model. PUBLIC HEALTH RELEVANCE: A mammalian conceptus must convince its mother's immune system to accept it. When the fetus fails to induce maternal tolerance, the outcome is either immune-mediated abortion or the development of abnormal placentation that can result in problems later in pregnancy. The incidence of immune-mediated abortion and placental insufficiency in both humans and cattle are greatly increased with the use of assisted reproductive technologies such as in vitro fertilization. In this study bovine somatic cell nuclear transfer pregnancies, which normally have a high rate of first trimester spontaneous abortions, will be used to study how communications between the conceptus and maternal immune system break down when embryos are manipulated in vitro.